How did the rijal scholars know if person x is reliable?

[Hugo Boss]

Assalamu A'laykum Wa Rahmatullahi Wa Barakatu, I have been wondering, how did our scholars like Sheikh Al Tusi (ra) know if person x is reliable or not?? And the same thing goes for the Sunni scholars, but I'd rather know how our scholars knew it first. I have been searching and searching, but I haven't found any luck, but that's probably because most of the stuff we have in our text is in Arabic, so its quite hard for a person like me who isn't that great at Arabic to understand what I am reading.  Jazakullahu feekum

[iraqi_shia]

They check if the person is known, and what their reputation is.

The science of hadith is not exact, but one where if you have an overwhelming weight of evidence that says such a narration is true, then it should be taken that way.

Eg, one person may occasional lie, or make mistakes. However if 20 people who are known to be reliable, say the same thing, then its very likely to be true.

 

[Panzerwaffe]

9 hours ago, Hugo Boss said:

Assalamu A'laykum Wa Rahmatullahi Wa Barakatu, I have been wondering, how did our scholars like Sheikh Al Tusi (ra) know if person x is reliable or not?? And the same thing goes for the Sunni scholars, but I'd rather know how our scholars knew it first. I have been searching and searching, but I haven't found any luck, but that's probably because most of the stuff we have in our text is in Arabic, so its quite hard for a person like me who isn't that great at Arabic to understand what I am reading.  Jazakullahu feekum

Biographical literature was important to make that determination 

[Hugo Boss]

hmm... But like, how were they able to check the biographies of them? Or how did they get their hands on these documents? Etc. 

[AMR5]

The Islamic seminaries are not a one off thing, there is a whole legacy of knowledge going on where they learn the research and opinions of the scholars before they who learned it before them and so on. Otherwise the Ilm of Rijal would have been impossible in a vacuume.